1. Field of the invention
This invention relates to skin care compositions containing stable, discrete microdroplets of an oil in water stabilized by a water-soluble polymer solution, and more particularly to new and improved cosmetic compositions for the care of the skin.
2. Description of the Prior Art
The unique properties of many oils make it desirable to include them in aqueous-based cosmetic compositions. For example, cosmetically-active materials such as silicone oils, fluids and gums, mineral oils, and water-insoluble organic esters such as isopropropyl palmitate and isopropyl myristate, are particularly useful in cosmetic formulations for the hair and skin. In these compositions, the lubricity properties of the cosmetically-active materials impart conditioning action for the user. However, such oils are immiscible with water which makes it very difficult to maintain a stable aqueous dispersion without rapid separation of the composition into oil and water phases. To solve the problem of providing effective dispersibility of such materials in water, it has been necessary in the past to include a surfactant in aqueous cosmetic compositions containing cosmetically-active oils in order to maintain dispersed droplets of the oil in the aqueous solution. However, the use of surfactants increases the cost of the product and may effect the quality of the composition. In addition, even with a surfactant present, the stability of the dispersion is often not completely satisfactory. See, for example, U.S. Pat. Nos. 3,957,970; 4,472,375; 4,559,227; 4,586,518; 4,728,457; 4,741,855; 4,749,565; 4,749,732; 4,788,006; and 4,849,127.
However, these and other processes have not provided a composition in which cosmetically active oils, such as silicone oils, are present as a stable dispersion in an aqueous medium. Nor does the prior art suggest a procedure for allowing such oils to maintain themselves in stable condition in an aqueous cosmetic formulation.
Accordingly, it is an object of the present invention to provide a cosmetic composition having a stabilized oil in water therein, preferably in the form of microdroplets, which can be maintained discretely and for an extended period of time.
Another object of this invention is to provide a method for preparing an aqueous skin care composition which includes stable, discrete microdroplets of a silicone oil dispersed therein.
Still another object of the present invention is to provide a method of preparing a skin care composition in which microdroplets of silicone oil are homogeneously distributed in the composition.
Yet another object is to provide a skin care composition in which stable, dispersed microdroplets are prepared by in situ polymerization of a water-soluble vinyl monomer, such as vinylpyrrolidone, in the presence of dispersed droplets of a water-insoluble oil, such as silicone oil, in water.
Among the other objects of the invention is to provide a skin care formulation containing stable, discrete microdroplets of a cosmetically-active oil stabilized in an aqueous solution of in situ polymerized vinylpyrrolidone.
These and other objects and features of the invention will be made apparent from the following description thereof.